This Information Applies To: Agilent ICP-MS systems (7700/7800/7850/7900/8800/8900)
Elevated oxide ratio values are defined as greater than 1.5% for x-lens configuration or greater than 3% for s-lens configuration. Possible causes are contamination, or a fault with the sample introduction system.
The Oxide Ratio (%) is defined as: mass 156 (CeO) / 140 (Ce) x 100
Gd, Dy, CdAr, SnAr, and SeSe are some examples of contaminants/interferences that contribute to elevated counts on mass 156.
Steps to Follow
Check for Contamination
Prepare or pour fresh tuning solution in 1% HNO3 (1 ppb tuning solution for standard configuration, 10 ppb tuning solution for ISIS 3 configuration)
Place the internal standard line into a fresh 1% HNO3 rinse solution (for standard configuration) or place the carrier line into a fresh 1% HNO3 rinse solution (for ISIS 3 configuration).
Light plasma and perform startup tasks: Torch Axis, EM, Plasma Correction, Standard Lenses Tue, Resolution/Axis, and Performance Report.
Check the oxide ratio from the startup performance report. If the oxide ratio has decreased, either the tuning solution or rinse solution was contaminated.
If the oxide ratio has not decreased, it is possible that the de-ionized water source, or HNO3 source is contaminated. Prepare again the tuning solution and 1% HNO3 rinse solution with a second source of de-ionized water and HNO3, then retest.
If the high oxide ratio occurred after replacing the argon, the contamination could be in the argon gas. Contact your gas supply company and test a different source of argon.
It is also possible that the sample introduction system is contaminated. Clean the nebulizer, spray chamber, torch, cones, and lens stack as per the Agilent ICP-MS Hardware Maintenance Manual. See the ICP-MS MassHunter Help and Learning Center. See the article Access Agilent ICP-MS User Manuals with MassHunter 5.x for accessing the Help and Learning Center.
Check for Sample Introduction Fault
If the high oxide ratio occurred after sample introduction maintenance, please confirm that the torch, spray chamber, nebulizer, cones, and lenses have been reinstalled properly.
The oxide ratio should increase when you increase the nebulizer (carrier) gas flow. Check the nebulizer gas connection and replace the nebulizer if needed.
Verify that the cones are in good condition. Poor orifice shape or size, or excessively dirty cones can cause elevated oxide ratio. Replace the skimmer and sampler cone if needed.
Learn how to effectively troubleshoot your Agilent ICP-MS System:
Agilent 7800/7850/7900 ICP-MS with MassHunter e-learning course available from Agilent education